How do I collect monies owed by my wholesale customer who sold their store? Escrow has closed but the funds are still not disbursed yet.

Your customer continues to be responsible for the obligation even though the business was sold. If the transaction was  handled properly, the purchaser  most likely insulated itself from the obligation upon close of the escrow(unless it agreed in writing in its purchase contract to be responsible for the debts of the seller). You may have a remedy (once a judgment is obtained) for collection should the buyer be paying the seller over time. This remedy would require you to issue a third party levy against the buyer to capture any of the funds that might still be due and owing to the seller.